So far, Long-Term Evolution (LTE) operates based on deployment in a licensed carrier. Along with the evolution of LTE, some enterprises (e.g. Qualcomm from America) have put forward a subject of proposals on the deployment of LTE in unlicensed carriers in the second half of 2013. However, this subject has not been accepted or approved by LTE yet.
In the view of Qualcomm, the reason why this subject should be approved is mainly as follows. As data services are increasing sharply, a licensed spectrum will not be capable of bearing such a great quantity of data before long. Thus, Qualcomm suggests deploying LTE in unlicensed carriers to offload the traffic in licensed carriers using an unlicensed spectrum.
Additionally, unlicensed spectrum has many advantages. For example, unlicensed spectrum has the following features and advantages:
free/cheap (the expenditure on spectrum resources is zero because it is not needed to buy an unlicensed spectrum);
low access requirement and low cost (apart from individuals and enterprises, devices of manufactures can participate in deploying an unlicensed spectrum);
sharable resources (in a case where a plurality of different systems operate in an unlicensed spectrum or different operators of the same system operate in an unlicensed spectrum, some resource sharing methods may be used to improve spectrum efficiency);
multiple wireless access technologies (multiple wireless access technologies may follow different communication standards, making it difficult to realize their cooperation and generating various network topologies);
many wireless access sites (a great number of users, difficult cooperation and high cost on centralized management); and
many applications (it is revealed by data that a plurality of services, for example, Machine-to-Machine (M2M) and Vehicle-to-Vehicle (V2V)), can operate in an unlicensed spectrum).
The foregoing features enables unlicensed carrier to become a potential important evolution direction of wireless communication systems, however, unlicensed carrier also has many problems. For example, various wireless systems may exist in an unlicensed carrier, it may be difficult to coordinate these wireless systems, and moreover, the interference among these wireless systems may be serious.
In a case where an LTE system operates in an unlicensed carrier, when an LTE base station occupies resources of an unlicensed carrier, how to perfectly coordinate an occupation time length and subframe scheduling of LTE to avoid resource waste should be settled, and how to set an occupation time length more reasonably under constraints of a contention backoff mechanism suitable for LTE should also be settled.
No effective solutions have been proposed to address the problem that occupation of an unlicensed carrier is not properly achieved.